Design, synthesis, spectroscopic characterization, and theoretical studies of Mn(II), Co(II), Ni(II), and Cd(II) Schiff base complexes derived from 4-Hydroxycoumarin, Glycine, and Metformin

Abstract

In this work, the synthesis, characterisation and preparation of several new Mn(II), Co(II), Ni(II) and Cd(II) complexes with Schiff base ligands prepared from 4-hydroxycoumarin, The ligands and their respective metal complexes were synthesised in 1:1:1 metal to ligand molar ratio and characterised by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), UV–Visible spectroscopy, molar conductivity measurements, magnetic susceptibility studies and atomic absorption spectroscopy. In addition, theoretical calculations were carried out using GaussView05/Gaussian09 software with the semi-empirical PM6 method to support the experimental findings. FT-IR spectral analysis revealed that the coumarin-based Schiff base ligand acts as a bidentate chelating agent through the azomethine nitrogen (C=N) and the carboxylate oxygen (COO⁻) atoms, resulting in the formation of stable five-membered chelate rings with the metal ions. S hifting of N–H and C=N vibrational bands suggested the involvement of amine and imine nitrogen atoms in the coordination of the metal, and supported the complexation of metformin. The electronic spectra and magnetic moment data were in support of the proposed coordination geometries around the metal centres. Molar conductivity measurements in DMSO indicate that most the complexes behave as electrolytes. The theoretical results were in good agreement with the experimental data, providing deeper insight into the electronic structure and stability of the synthesized complexes. In conclusion the results proved the efficiency of coumarone, and metformin based Schiff base ligands in the field of coordination chemistry and suggested that their divalent metal complexes may be promising in future applications in the field of chemical and materials sciences.